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Performance-Based Specification for Binders Used in Chip Seals (and other Surface Treatments)

Historically, emulsion specifications have been parochial, as the availability (i.e. type of asphalt available and local suppliers capabilities) has generally driven the specifying agencies' decision on which emulsions to specify. As suppliers, sources, etc. change, new emulsion specifications are developed and promulgated. Today's technology has brought more manufacturing choices and capability to agencies whereby a "performance-based" specification is desired. Binder specifications for chip seal applications and other surface treatments include emulsions and hot applied liquids. These specifications do not incorporate standard performance grading for the base asphalt. Most emulsion specifications continue to use viscosity-graded asphalt binders or penetration-based specifications. A specification that incorporates a standard grading system will serve to more uniformly describe asphalts and base asphalt for asphalt emulsions specified by federal, state, and local agencies. Applying a more uniform grading system may reduce testing, increase the collaboration between states, and improve the ability to compare actual field performance to this "performance" graded specification. This new specification needs to address testing at temperatures normally seen by surface treatment applications such as chip retention, fatigue at room temperature, ability to penetrate cracks of varied widths, and adhesion at high and low temperatures, and include climate and traffic in the binder selection process. A chip seal and surface treatment binder specification should be applied to both hot-applied binders and emulsion residues. Asphalt emulsion requirements must include a mechanism for acquiring the emulsion residue such that this residue is representative of the binder on the road.